textproduct: Albany

SYNOPSIS

Mostly cloudy but milder weather is expected today along with isolated to scattered rain showers. A cold front crosses the region tonight bringing blustery and colder weather for the remainder of the week along with lake effect snow showers. Heavy snow accumulations are expected across portions of the Adirondacks and possibly the Mohawk Valley. Drier weather returns by Saturday with high pressure returning before another system brings mixed rain and snow on Sunday.

SHORT TERM /THROUGH FRIDAY NIGHT/

Key Messages:

- A period of lake effect snow is expected later Thursday through Friday across portions of the Adirondacks and Mohawk Valley. Snowfall amounts of 6 to 12 inches are expected in the most persistent lake effect bands.

- A Lake Effect Snow Warning is in effect for Northern Herkimer and Hamilton County from Thursday afternoon into Friday night. A Winter Storm Watch remains in effect for Southern Herkimer County from Thursday Afternoon into Saturday Morning.

- Wind gusts between 30 and 40 mph on Thursday and Friday could lead to areas of blowing and drifting snow.

Discussion:

A warm front is lifting northward across the region this morning. The steadiest rain has departed to the east but favorable upper level lift within the warm sector will support additional isolated to scattered showers through this afternoon. Later this afternoon into the evening hours, a cold front will approach from the west. Along with front, another area of rain showers will cross parts of the area. There could be some brief periods of more moderate rain with this activity. Pending surface temperatures, precipitation could change over to snow across parts of the southwest Adirondacks before ending. Despite a mostly cloudy day, temperatures should reach the 50s to lower 60s for many areas, except in the upper 40s to around 50 across the Adirondacks, which is about 10-15 degrees above normal high temperatures for late November.

As the front crosses, upper level troughing builds into the region for the remainder of the week with a nearly vertically stacked low pressure system positioned across Quebec. Moist, cyclonic flow and the arrival of colder air will support the development of lake effect snow. The wind flow will start out southwesterly which will result in mostly dry weather to start Thanksgiving Day with bands oriented west of our CWA. By the afternoon, the flow will become more west to west-southwesterly which will shift the bands slightly south and eastward into parts of the Adirondacks. Some fragments of the lake effect bands off Erie could reach parts of the Mohawk Valley by the afternoon hours as well. By Thursday night into Friday, the passage of an upper level shortwave will shift the winds to a more west-northwest to northwesterly direction for Friday. This will shift the band southward and become oriented across portions of the Mohawk Valley and eastern Catskills. Lake effect snow across the Adirondacks will then transition to upslope snow showers for Friday. There is some uncertainty with the overall placement of the Lake Ontario snow band on Friday. Two scenarios are in play which include the snow band oriented right over the NY Thruway corridor or just to the south. Where the band does set up, additional moderate to heavy snowfall accumulations are likely to occur due to the presence of moderate lake induced instability and a multi-lake connection extending all the way back to Lake Superior. Fragments of the snow band will likely extend into portions of the Hudson Valley with upslope snow showers across the southern Greens and Berkshires. High pressure building into the region on Saturday will gradually shut off the lake effect response.

In the most persistent lake effect bands, 6-12 inches of snow is expected. Confidence in these amounts was high enough to upgrade Northern Herkimer and Hamilton Counties to a Lake Effect Snow warning on this shift, plus with the lake effect snow starting on Thursday. Due to decreased confidence on the overall orientation of the snow band across the Mohawk Valley and likely not beginning until early Friday, have maintained the Winter Storm Watch for Southern Herkimer County. Where the band does sets up, warning level snowfall is likely to fall. Pending the orientation of the snow band, additional Winter Weather headlines may be needed later in time for Fulton, Montgomery and/or Schoharie counties.

Outside of the lake-effect it will be blustery and colder with highs in the lower 30s to lower 40s on Thanksgiving Day and upper 20s to upper 30s on Friday. Wind gusts between 30-40 mph later this week (strongest on Friday) will add to the chill in the air and also lead to areas of blowing and drifting snow.

LONG TERM /SATURDAY THROUGH TUESDAY/

As mentioned above, surface high pressure and weak upper level ridging builds over the region to start the weekend. This will shut off the lake effect snow and result in a dry start to the weekend. It will remain on the chilly side with highs only in the mid-20s to upper 30s, but there will be less wind compared to the previous two days. Another low pressure system tracking across the Great Lakes will bring another round of precipitation for Sunday. With temperatures rebounding into the 30s and 40s, mixed rain and snow is expected with this system. Snow would be favored for higher elevations. The cold front associated with this systems passes through by late Sunday which could lead to a mainly dry start to next week with high pressure returning. However, another wave of low pressure may form along the front bringing the potential for additional precipitation by Tuesday or Wednesday of next week, pending the overall timing and track of this system.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

Through 18z Thursday...MVFR to IFR and even patchy LIFR conditions prevail across the TAF sites this afternoon as ample low-level moisture sits beneath an inversion. Some improvements can be anticipated here over the next couple of hours however, as visible satellite imagery shows some patchy clearing especially in downsloped areas near ALB and PSF. TEMPO groups were added to the TAFs accordingly.

Patchy clearing won't be long lasting this afternoon as clouds race ahead of a potent incoming cold front and upper-level disturbance. A batch of rain showers is anticipated as a result of these features as well later this evening, forcing the return to MVFR to IFR conditions almost everywhere. However, rapidly drying air behind the front should translate to rapid improvements in ceiling height behind the showers. Therefore, VFR conditions, once realized late tonight, should remain in place through much of the remainder of the 18z TAF period.

Winds will begin the period out of the south to southwest a light speeds under 10 kt. However, the passage of the cold front will force the rapid veer to the west to northwest through the end of the period. At this point, winds will become breezy with sustained speeds reaching 8 to 12 kt with paired gusts of 15 to 25 kt.

Outlook...

Thursday Night: Low Operational Impact. Breezy. Slight Chance of SHSN. Friday: High Operational Impact. Windy With Gusts To 38 kts. Likely SHSN. Friday Night: Low Operational Impact. Breezy. Slight Chance of SHSN. Saturday: Low Operational Impact. Breezy. NO SIG WX. Saturday Night: Low Operational Impact. NO SIG WX. Sunday: High Operational Impact. Likely SHRA...SHSN. Sunday Night: Moderate Operational Impact. Chance of SHRA...SHSN. Monday: Low Operational Impact. NO SIG WX.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...Lake Effect Snow Warning from 4 PM Thursday to 1 AM EST Saturday for NYZ032-033. Winter Storm Watch from Thursday afternoon through Saturday morning for NYZ038. MA...None. VT...None.